From 2558e76b5d8596ac411d7170b8ea5db299911e2d Mon Sep 17 00:00:00 2001
From: goyuken <goyuken@4bbf4f03-6f44-549e-7e59-35d4b0962838>
Date: Mon, 23 Dec 2013 20:34:02 +0000
Subject: [PATCH] fix rewind on N64, gpgx.debug

---
 BizHawk.Client.Common/movie/MovieRecord.cs       |  2 +-
 BizHawk.Client.EmuHawk/MainForm.Rewind.cs        | 15 +++++++++++----
 BizHawk.Emulation.Common/Interfaces/IEmulator.cs |  4 ++++
 3 files changed, 16 insertions(+), 5 deletions(-)

diff --git a/BizHawk.Client.Common/movie/MovieRecord.cs b/BizHawk.Client.Common/movie/MovieRecord.cs
index 5e0529a802..e4e655730d 100644
--- a/BizHawk.Client.Common/movie/MovieRecord.cs
+++ b/BizHawk.Client.Common/movie/MovieRecord.cs
@@ -51,7 +51,7 @@ namespace BizHawk.Client.Common
 		public void CaptureSate()
 		{
 			Lagged = Global.Emulator.IsLagFrame;
-			_state = Global.Emulator.SaveStateBinary();
+			_state = (byte[])Global.Emulator.SaveStateBinary().Clone();
 		}
 
 		public void ClearInput()
diff --git a/BizHawk.Client.EmuHawk/MainForm.Rewind.cs b/BizHawk.Client.EmuHawk/MainForm.Rewind.cs
index a518a3a455..005b64001f 100644
--- a/BizHawk.Client.EmuHawk/MainForm.Rewind.cs
+++ b/BizHawk.Client.EmuHawk/MainForm.Rewind.cs
@@ -258,7 +258,11 @@ namespace BizHawk.Client.EmuHawk
 		class RewindThreader : IDisposable
 		{
 			//adelikat: tweak this to test performance with threading or not with threading
-			public static bool IsThreaded = true;
+			// natt: IEmulator.SaveStateBinary() returns a byte[] but you're not allowed to modify it,
+			// and if the method is called again, the data from a previous call could be invalidated.
+			// GPGX and N64 make use of this property.  if you set IsThreaded = true, you'll need to Clone() in many cases,
+			// which will kill N64 for sure...
+			public static bool IsThreaded = false;
 
 			MainForm mf;
 
@@ -419,7 +423,7 @@ namespace BizHawk.Client.EmuHawk
 		public void DoRewindSettings()
 		{
 			// This is the first frame. Capture the state, and put it in LastState for future deltas to be compared against.
-			LastState = Global.Emulator.SaveStateBinary();
+			LastState = (byte[])Global.Emulator.SaveStateBinary().Clone();
 
 			int state_size = 0;
 			if (LastState.Length >= Global.Config.Rewind_LargeStateSize)
@@ -557,8 +561,11 @@ namespace BizHawk.Client.EmuHawk
 				TempBuf = new byte[TempBuf.Length * 2];
 				goto RETRY;
 			}
-			
-			LastState = CurrentState;
+
+		if (LastState != null && LastState.Length == CurrentState.Length)
+			Buffer.BlockCopy(CurrentState, 0, LastState, 0, LastState.Length);
+		else
+			LastState = (byte[])CurrentState.Clone();
 			var seg = new ArraySegment<byte>(TempBuf, 0, (int)ms.Position);
 			RewindBuf.Push(seg);
 		}
diff --git a/BizHawk.Emulation.Common/Interfaces/IEmulator.cs b/BizHawk.Emulation.Common/Interfaces/IEmulator.cs
index 924a78bccf..4c6cd32426 100644
--- a/BizHawk.Emulation.Common/Interfaces/IEmulator.cs
+++ b/BizHawk.Emulation.Common/Interfaces/IEmulator.cs
@@ -111,6 +111,10 @@ namespace BizHawk.Emulation.Common
 		void LoadStateText(TextReader reader);
 		void SaveStateBinary(BinaryWriter writer);
 		void LoadStateBinary(BinaryReader reader);
+		/// <summary>
+		/// save state binary to a byte buffer
+		/// </summary>
+		/// <returns>you may NOT modify this.  if you call SaveStateBinary() again with the same core, the old data MAY be overwritten.</returns>
 		byte[] SaveStateBinary();
 
 		/// <summary>